The present invention is related to an image scanner capable of scanning reflective and penetrative documents, and more particularly, to a flat bed image scanner capable of scanning reflective and penetrative documents.
In the past, image scanners are principally divided into two types according to different scanning objects. One is the reflective document image scanner for scanning reflective documents, such as documents and papers. The other is the penetrative document image scanner for scanning positive and negative films, such as slides and films. These two types of image scanners have different requirement for resolution (generally, the penetrative document image scanner has higher requirement for resolution than the reflective document image scanner), therefore, their cost is very different. Typically, the reflective document image scanner is usually made in the form of flat bed scanner, and the penetrative document image scanner is made in the form of film scanner.
However, with the development of continually increasing resolution and application range for a flat bed scanner, the function of scanning transparent document has been merged into the flat bed scanner to increase its additional value. In the present market, there are two main designing points of a flat bed scanner which have the function of scanning transparent document. One is implemented by using the same optical system design to co-operate with the transmission mechanism and to switch different camera lens or charge-coupled devices (CCD). The other is performed by using different optical system design to co-operate with the transmission, mechanism and the same camera lens or CCD. The former will cause the increasing of error variability and lead to an extremely low yield if using the transmission mechanism and switching different camera lens or CCD. The later will be difficult to practice when considering the cost and the image quality if using different optical system design to co-operate with the transmission mechanism and the same camera lens or CCD. It is because that the producer must choose the CCD with higher density and larger numbers of pixels to considerate both sides of the high resolution scanning image quality of a small-sized film and the required pixel number of a large-sized paper document. Take the A4-sized CCD with resolution of 3600 dpi (dots per inch) as an example, the number of pixel is about 30600 points and the cost price is about 50 to 60 times compared to the CCD with 600 dpi, and is about 15 to 20 times compared to the CCD with 1200 dpi. In that case, the cost of product is too high. If we choose the cheaper CCD, under the designing construction described above, the high quality image scanning effect of a small-sized film can not be achieved.
It is an object of the present invention to provide an image scanner capable of scanning reflective and penetrative documents by using a simple and effective design of optical system and transmission module.
It is another object of the present invention to provide an image scanner capable of scanning reflective and penetrative documents, thereby expanding its application.
According to the present invention, the image scanner includes a housing, a supporting base, a first scanning platform, a first light transmitting device, a first photoelectric sensing element, a second scanning platform, a second light transmitting device, and a second photoelectric sensing element. The supporting base is mounted in the housing and moves along the first direction while the scanning operation is performed. The first scanning platform is mounted on the housing for placing thereon the reflective document to be scanned. The first light transmitting device is mounted fixedly on the supporting base for focusing and transmitting light signal reflected from the reflective document. The first photoelectric sensing element is mounted fixedly on the supporting base and has a first number of pixel sensing points for receiving the reflected light signal and converting the received light signal into electric signal. The second scanning platform is mounted in the housing for placing thereon the penetrative document to be scanned. The second light transmitting device is mounted fixedly on the supporting base for focusing and transmitting light signal penetrating through the penetrative document. The second photoelectric sensing element is mounted fixedly on the supporting base and has a second number of pixel sensing points for receiving the penetrating light signal and converting the penetrating light signal into electric signal, wherein the first number is larger than the second number.
Preferably, the housing is a flat bed image scanner housing.
Preferably, the first photoelectric sensing element and the second photoelectric sensing element are accomplished by charge-coupled devices (CCD).
Preferably, the first light transmission device includes a first reflective mirror module mounted fixedly on the supporting base for reflectively transmitting the reflected light signal from the reflective document, and a first lens module mounted fixedly on the supporting base for focusing the reflected light signal reflected from the first reflective mirror module to the first photoelectric sensing element to be received.
Preferably, the second light transmission device includes a second reflective mirror module mounted fixedly on the supporting base for reflectively transmitting the penetrating light signal from the penetrative document, and a second lens module mounted fixedly on the supporting base for focusing the reflected light signal reflected from the second reflective mirror module to the second photoelectric sensing element to be received.
Preferably, the reflective and penetrative documents are a paper document and a film.
Preferably, the image scanner further includes a first light source mounted fixedly on the supporting base for providing a light source to the first scanning platform while the scanning operation of the reflective document is performed.
Preferably, the image scanner further includes a second light source mounted fixedly on the supporting base for providing a light source to the second scanning platform while the scanning operation of the penetrative document is performed.
Preferably, the image scanner further includes a second light source mounted fixedly on the housing, and which is made of background light source module for providing a light source to the second scanning platform while the scanning operation of the penetrative document is performed.
Preferably, the image scanner further includes a third light source mounted above the first scanning platform for providing a light source to penetrate a second penetrative document placed on the first scanning platform while the scanning operation of the second penetrative document is performed.
Preferably, the penetrating light signal from the second penetrative document is focused by the first light transmission device and transmitted to the first photoelectric sensing element.
Preferably, the size of the reflective document is larger than that of the penetrative document.
Preferably, the size of the reflective document is larger than that of the penetrative document.
Preferably, the resolution of the second light transmission device is better than that of the first light transmission device.
The foregoing and other features and advantages of the present invention will be more clearly understood through the following descriptions with reference to the drawings, wherein: